È noto per aver doppiato Dio Brando in Le Bizzarre Avventure di JoJo, Zeke Jaeger ne L'Attacco dei Giganti ed Excalibur in Soul Eater.
Carriera Koyasu è parte del gruppo musicale Weiss, composto dai quattro principali doppiatori della serie Weiss Kreuz (Koyasu, Shinichiro Miki, Tomokazu Seki e Yuuki Hiro). Ha fatto parte dell'agenzia Production Baobab, ma in seguito ha fondato una propria nel 1998 chiamata T's Factory.
Per via della sua voce bassa e profonda, Koyasu interpreta principalmente ruoli da antagonista o da bishōnen solitario, benché proprio per questo in anni più recenti gli sono stati assegnati spesso ruoli parodistici o comici. Secondo quanto detto dalla mangaka Hisaya Nakajo, il personaggio di Masao Himejima di Hana-Kimi è stato creato proprio pensando alla voce di Koyasu.
Koyasu utilizza lo pseudonimo Hayato Jumonji, quando doppia anime hentai.
Koyasu, inoltre, è un doppiatore molto riservato ed infatti non ha mai rilasciato interviste.
Doppiaggio Anime Air Master (Fukamichi) Angel Links (Warren) Angel Sanctuary (Sakuya Kira) Angelique (Olivie) Arakawa Under the Bridge (Sister) Area 88 (Shin Kazama) Argento Soma (Dan Simmonds) Aries (Minos) Assassination Classroom (Gastro) Baccano! (Luck Gandor) Baki (Hector Doyle) Beast Wars (Convoy) Betterman (Lamia) Beyblade (Balkov) Bobobo-bo Bo-bobo (Bobobo-bo Bo-bobo) Bleach (Pesche Guatiche) Captain Tsubasa: Road to 2002 (Adult Kojiro Hyuga) Chrome Shelled Regios (Karian Loss) City the Animation (Dr. Adatara) Date A Live (Kyouhei Kannazuki) Demonbane (Winfield) Demon Slayer - Kimetsu no yaiba (Demone delle mani) DNA² (Ryuji Sugashita) Dragon Drive (Rokkaku) Excel Saga (Il Palazzo) Final Fantasy: Unlimited (Pist Shaz the 11th) Fire Emblem (Nabarl) Fire Force (Excalibur) Food Wars! - Shokugeki no Soma (Gin Dōjima) Full Metal Panic! (Zaiede) Fullmetal Alchemist (Lujon) Fullmetal Alchemist: Brotherhood (fratello di Scar) Fushigi yûgi (Hotohori) Gad Guard (Takenaka) Gate Keepers (Choutarou Banba) Gestalt (Father Oliver) Get Backers (Juubei Kakei) Gintama (Takasugi Shinsuke) Gravitation (Sakano) Guilty Crown (Shibungi) Gungrave (Balladbird Lee) Hakushaku to yōsei (Kelpie) Hanasakeru Seishōnen (Quinza) HappinessCharge Pretty Cure! (Oresky) Harlock Saga (Fasolt) Hell Girl (Yoshiyuki Honjō) Hello World (Tsunehisa Senko) Hellsing (Luke Valentine) Arslan Senki (Varnef) Hungry Heart: Wild Striker (Kanō Seisuke) Hunter × Hunter (serie animata 2011) (Dalzollene) I Cavalieri dello zodiaco - Saint Seiya - Hades (Rhadamante della Viverna) I Cavalieri dello zodiaco - The Lost Canvas (Veronica di Nasu) I'm the Evil Lord of an Intergalactic Empire! (La Guida) Infinite Dendrogram (Maise) Initial D (Ryosuke Takahashi) InuYasha (Gatenmaru) Jujutsu kaisen - Sorcery Fight (Toji Fushiguro) Kagihime Monogatari Eikyū Alice Rondo (Alternate L. Takion) Kaguya-sama: Love is War (Papa Shirogane) Kaleido Star (Fool) Kamisama Kiss (Kirakaburi) Ken il guerriero - La trilogia (Kenshiro) Keroro (Kururu) K.O. Century Beast Warriors (Bud Mint) Koutetsu Sangokushi (Shoutatsuryou Koumei) Kuragehime (Hanamori Yoshio) The Law of Ueki (Li Ho) L'attacco dei giganti (Zeke Jaeger) Le bizzarre avventure di JoJo: Phantom Blood (Dio Brando) Le bizzarre avventure di JoJo: Stardust Crusaders (Dio Brando) Le bizzarre avventure di JoJo: Stone Ocean (Dio Brando) Lemon Angel Project (Shinya Himuro) Loveless (Ritsu Minami) Macross 7 (Gamlin Kizaki) Magic User's Club (Ayanojyo Aburatsubo) Mahoromatic (Ryuuga Toh) Majin Tantei Nougami Neuro (Nougami Neuro) Major (Shigeharu Honda) Mamoru-kun ni Megami no Shukufuku wo! (Johan Deiter Rudiger) Mahō Sensei Negima! (Nagi Springfield) Majutsushi Orphen (Flameheart) Majutsushi Orphen Revenge (Flamesoul) Meine Liebe (Isaac Cavendish) Meine Liebe Wieder (Isaac Cavendish) Mobile Suit Gundam SEED (Mu La Flaga) Mobile Suit Gundam SEED Destiny (Mu La Flaga/Neo Roanoke) Mobile Suit Gundam Wing (Milliardo Peacecraft) / (Zechs Merquise) The Mythical Detective Loki Ragnarok (Mysterious Thief Freyr) Myself; Yourself (Syusuke Wakatsuki) Nazca (Masanari Tate) Neon Genesis Evangelion (Shigeru Aoba) Needless (Adam Blade) Nisekoi (Claude Ringheart) One Piece (Aokiji/Kuzan) Ouran High School Host Club (Ryoji "Ranka" Fujioka) Overlord (Nigun Grid Luin) Overman King Gainer (Asuham Boone) Papa to Kiss in the Dark (Takayuki Utsunomiya) Persona -trinity soul- Ryō Kanzato Planetes (Yuri Mihairokoh) Pocket Monsters (Kosaburo) Pretear - La leggenda della nuova Biancaneve (Tanaka) Pretty Cure (Takashi Misumi) Pretty Cure Max Heart (Takashi Misumi) Princess lovers (Vincent Van Hossen) Psycho-Pass (Talisman) Ragna Crimson (Grymwelte) Ragnarok the Animation (Keough) Ranma ½ (Daisuke) (after Daiki Nakamura) Re:Zero (Roswaal L. Mathers) Red Garden (Hervé Girardot) Ro-Kyu-Bu (Subaru's Dad) Rosario + Vampire (Narrator) Saban's Adventures of the Little Mermaid (Prince Justin) Saber Marionette J (Mitsurugi Hanagata) Saiunkoku Monogatari (Sakujun Sa) Sakura Wars (Yūichi Kayama) Samurai 7 (Ukyo, Amanushi) Samurai Champloo (Umanosuke) Samurai Deeper Kyo (Hatori Hanzo, Hotaru) Seiken Tsukai No World Break (Charles Saint Germain) Seikimatsu Occult Gakuin (JK) Sengoku Basara (Sarutobi Sasuke) Seto no Hanayome (Shark Fujishiro) Shaman King (Faust VIII) Shin Koihime Musou (Ukitsu (Yu Ji)) SK8 the Infinity (Ainosuke Shindo / Adam) Slayers (Rezo, Copy Rezo) Slayers - La città dei Golem (Huey) Soul Eater (Excalibur) Spider Riders (Igneous) Suicide Squad Isekai (Peacemaker) Suki na Mono wa Suki Dakara Shōganai! 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Videogiochi Anima Mundi: Dark Alchemist (Bruno Glening) Another Century's Episode 2 (Zechs Merquise) Ar tonelico II (Alfman Uranous) Arc Rise Fantasia (Weiss) ASH: Archaic Sealed Heat (Dan) Atelier Yumia: The Alchemist of Memories & the Envisioned Land (Corleonis) Bayonetta 2 (Padre Balder (giovane)) Bleach: Rebirth of Souls (Pesche Gatiche) Bravely Default (Braev Lee) Bravely Second: End Layer (Braev Lee) Breath of Fire 6 (Masamune) Catherine (Jonathan Ariga) Catherine: Full Body (Jonathan Ariga) Captain Tsubasa Dream Team (Rivaul) Code Vein II (Zenon Gryfgote) CROSS†CHANNEL (Hiroshi Sakuraba) Demonbane on PS2 (Winfield) Disgaea 2: Cursed Memories (Mr. Rabbit, Fubuki, Badass Overlord Zeta) Disgaea 4: A Promise Unforgotten (Zetta) Disgaea 5: Alliance of Vengeance (Red Magnus) Disgaea RPG (Red Magnus, Fubuki) Dissidia Final Fantasy: Opera Omnia (Seifer Almasy) Double Dragon Revive (Jimmy Lee) Dragalia Lost (Mordecai, Morsayati) Dragon Force II: Kamisarishi Daichi ni (Shepherd) Dragon Quest VIII: L'odissea del re maledetto (versione 3DS) (Dhoulmagus) Dragon Quest Rivals (Dhoulmagus) Dynasty Warriors: Gundam (Miliardo Peacecraft) Dynasty Warriors: Gundam 2 (Miliardo Peacecraft, Gym Ghingnham) Dynasty Warriors: Gundam 3 (Gym Ghingnham, Miliardo Peacecraft) Eiyuden Chronicle: Hundred Heroes (Dr. Kokito, Iugo) Everybody's Golf Hot Shots (Dino) Fantasy Life i: La ragazza che ruba il tempo (Klaus, Pierre) Fate/Extra CCC (Caster/Hans Christian Andersen) Fate/Grand Order (Caster/Hans Christian Andersen, Rider/Ozymandias, Caster/Mephistopheles) Fighting for One Piece (Aokiji/Kuzan) Final Fantasy Crystal Chronicles Remastered (Stiltzkin) Fire Emblem: Awakening (Lon'zu, Validar) Fire Emblem: Fates (Niles) Fire Emblem Heroes (Navarre, Saber, Lewyn, Pent, Garcia, Lon'zu, Validar, Niles, Seteth, Kagetsu) Fire Emblem Echoes: Shadows of Valentia (Saber) Fire Emblem Warriors (Navarre, Validar, Niles) Fire Emblem: Three Houses (Seteth) Fire Emblem Warriors: Three Hopes (Seteth) Fire Emblem: Engage (Kagetsu) Fire Emblem: Fortune's Weave (Seteth) Fist of the North Star: Ken's Rage (Rei) Fist of the North Star: Ken's Rage 2 (Rei) Galerians (Birdman) Granblue Fantasy (Lucius, Bobobo-bo Bo-bobo, Shinsuke Takasugi) Growlanser III: The Dual Darkness (Zion) Guilty Gear XX (Eddie) Guilty Gear Isuka (Eddie) Guilty Gear: Dust Strikers (Eddie) Guilty Gear Judgment (Eddie) Guilty Gear Xrd -SIGN- (Zato-1, Eddie) Guilty Gear Xrd -REVELATOR- (Zato-1, Eddie) Guilty Gear -STRIVE- (Zato-1, Eddie) Gundam Breaker 4 (Chaos) Hi-Fi Rush (Kale Vandelay) Homura Hime (Will of the World) I Cavalieri dello zodiaco - Hades (Rhadamante della Viverna) Illusion Connect (Barinas) Infinity Strash - Dragon Quest: The Adventure of Dai (Mistobaan) J-Stars Victory Vs+ (Bobobo-bo Bo-bobo, Neuro Nogami) JoJo's Bizarre Adventure: All Star Battle (Dio Brando) JoJo's Bizarre Adventure: Eyes of Heaven (Dio Brando, Diego Brando) JoJo's Bizarre Adventure: All Star Battle R (Dio Brando, Diego Brando) Jujutsu Kaisen Cursed Clash (Toji Fushiguro) Jump Force (Dio Brando) THE iDOLM@STER SP Takao Kuroi Initial D Street Stage (Ryosuke Takahashi) Keroro RPG: Kishi to Musha to Densetsu no Kaizoku (Kururu) Kingdom Hearts II (Seifer Almasy) League of Legends (Sett) Legasista (Volks Zaid) Like a Dragon: Infinite Wealth (Yutaka Yamai) Lux-Pain (Liu Yee) Magical Drop III (Hanged Man, Chariot, Hierophant) Magna Carta: Tears of Blood (Raul) Makai Kingdom: Chronicles of the Sacred Tome (Zetta) Marvel Tōkon: Fighting Souls (Wade Wilson/Deadpool) Master Detective Archives: Rain Code (Yakou Furio) Mega Man Legends 2 (Glyde, Guild Master) Metaphor: ReFantazio (More) Mighty No. 9 (Mr. Graham) Mind Zero (Yoichi Ogata) Mobile Suit Gundam SEED: Alliance vs. Z.A.F.T. (Mu La Flaga) Mobile Suit Gundam SEED Battle Destiny (Neo Roanoke/Mu La Flaga) Musashi: Samurai Legend (Gandrake) Muv-Luv (Takahashi Ichimonji, Naoya Sagiri) Muv-Luv Alternative (Takahashi Ichimonji, Naoya Sagiri) Nights of Azure 2: Bride of the New Moon (Joe, David, Malvasia (armatura)) Nioh 3 (Hiruko) Octopath Traveler II (Harvey) One Piece: Grand Battle! (Aokiji/Kuzan) One Piece: Unlimited Adventure (Aokiji/Kuzan) One Piece Unlimited Cruise 1: Il Tesoro Sommerso (Aokiji/Kuzan) One Piece Unlimited Cruise 2: Il Risveglio di un Eroe (Aokiji/Kuzan) One Piece: Pirate Warriors (Aokiji/Kuzan) One Piece: Unlimited Cruise SP 2 (Aokiji/Kuzan) One Piece: Romance Dawn (Aokiji/Kuzan) One Piece: Pirate Warriors 2 (Aokiji/Kuzan) One Piece: Unlimited World Red (Aokiji/Kuzan) One Piece: Pirate Warriors 3 (Aokiji/Kuzan) One Piece: Burning Blood (Aokiji/Kuzan) One Piece: World Seeker (Aokiji/Kuzan) One Piece: Pirate Warriors 4 (Aokiji/Kuzan) One Piece Odyssey (Aokiji/Kuzan) Persona 2: Innocent Sin (Tatsuya Suou) Persona 2: Eternal Punishment (Tatsuya Suou) Raidou Remastered: The Mystery of the Soulless Army (Shouhei Narumi) Remember11: The Age of Infinity (Satoru Yukidoh) Resonance of Fate (Sullivan) Rise of the Ronin (Kogoro Katsura) Saint Seiya: Brave Soldiers (Rhadamante della Viverna) Saint Seiya: Soldiers' Soul (Rhadamante della Viverna) Sakura Wars 2: Thou Shalt Not Die (Yuichi Kayama) Sakura Wars 3: Is Paris Burning (Yuichi Kayama)